Hall effect investigations taken on Si+-/N+-, C+-/N+- or Ne+-N+-co-implanted 4H-SiC layers and deep level transient spectroscopy investigations taken on Si+-implanted 4H-SiC layers provide experimental evidence for an electrically neutral defect complex formed during the annealing process at temperatures between 1400 degrees C and 1700 degrees C. This defect complex consumes nitrogen donors and an intrinsic Si containing defect species (interstitial Si or Si-antisite) or C-vacancies. At our present knowledge, we favor an (N-X-Si-Y)-complex.